Towards devising pilot experiments to establish parameter window for FSP of aluminum alloys

One of the major challenges encountered during friction stir processing (FSP) is the establishment of a process parameter window in order to achieve processed surfaces with an acceptable quality as it is an exhaustive task that involves enormous resources, time and efforts. Sometimes this task is so difficult that the trial may run into futility. This work belongs to a theme of FSP that is not much reported in the literature. This is a maiden work to lay a roadmap for the FSP parameter range in a quick and effective manner. The present study results from first-hand experiments performed to produce surface composites on AA6063 alloy using a mixture of SiC+Fe+Mn+Sn as reinforcement in such a manner that a novice professional can pan out ways to identify and classify irregularities/defects, associate them with the causes and obtain feasible parameter window. In this work, a methodology for identification and selection of optimum tool speed (rpm), processing speed and plunge depth has been demonstrated. The parameter window was established by analysing main surface irregularities associated with the parameters and taking corrective modification to eventually arrive at the feasible range. The established range was validated through an experiment performed with the parameters lying within the established window. The validation was supported with microstructural characterization, micro-hardness measurement, thermal analysis, corrosion analysis and the comprehensive analysis presented in this work has been done with the help of the image processing technique. Results show that grain refinement and homogeneous distribution of reinforcement present in the stir zone developed during FSP at the appropriate process parameters. Furthermore, grain refinement enhances the hardness by 28.29% and the corrosion resistance by 13.6%. The highest temperature i.e. 423.25°C is achieved on the advancing side of the processed zone